This invention relates to an actuator arrangement and in particular to an actuator arrangement suitable for use in an electrically driven thrust reverser system for use in moving components of the thrust reverser system between stowed and deployed positions.
One form of thrust reverser system includes a pair of part generally cylindrical cowls each being arranged to be driven between stowed and deployed positions by a plurality of linearly extendable actuators. Commonly, the actuators used in this application have been hydraulically driven. However, the use of electrically powered thrust reverser systems is becoming more common.
One form of electrically powered thrust reverser system includes a cowl moveable by a plurality of ball or roller screw type actuators, for example three such actuators may be provided. A single electrically powered motor is used to drive all of the actuators associated with the cowl, an appropriate gear box and drive transmission system being provided to distribute and transmit power to the actuators and to ensure that the actuators operate in synchronism with one another at the same speed.
In normal use, the actuators are driven at high speed over the majority of their length, the motor being controlled to reduce the speed at which the actuators are driven as the actuators approach their stowed and fully deployed positions so that, when the stowed and fully deployed positions are reached, movement can be safely arrested by claw stops provided in the actuators. The stops are configured so that the stops of all of the actuators associated with the cowl engage to arrest further movement simultaneously.
There is a requirement for the stops provided in the actuators to be able to arrest movement even if the motor fails to slow the rate of operation of the actuators as they approach the stowed and fully deployed positions, for example as a result of a control failure in the thrust reverser control system resulting in the occurrence of a so called powered runaway condition in which the motor continues to be driven at full speed as these positions are approached.
One way in which the stops can be designed to be able to arrest such movement is to increase the radial height of the stops so as to enable them to withstand greater loadings as would occur in such circumstances. However, doing so would result in the diameter of the tail tube of each actuator being increased. As the actuators are approximately 1 m long, increasing the diameter of the tail tube even by a relatively small amount can result in a significant increase in the weight of the actuator arrangement, which is undesirable.
It is an object of the invention to provide an actuator arrangement in which the problem outlined hereinbefore is overcome or of reduced effect.